Hi everyone, I am trying to obtain predictions from a smooth of vectors. I have successfully modeled the smooth vectors, using the following: test=gam(outcome~s(matb,by=mat,k=4)) summary(test) plot(test) Both matb and mat are matrices, each containing 7 columns. I am unsure of how to set up the prediction data frame given there are two matrices: I have tried creating two separate matrices (matpdat and matpdat2) containing the names of original columns in mat and matb and linking them with c(): matpdat=matrix(0,nrow=1,ncol=7) matpdat=data.frame(matpdat) names(matpdat)=c("lag.1.1","lag.2.1","lag.3.1","lag.4.1","lag.5.1","lag.6.1","lag.7.1") matpdat[1,1]=1 matpdat2=matrix(0,nrow=1,ncol=7) matpdat2=data.frame(matpdat2) names(matpdat2)=c("V53","V54","V55","V56","V57","V58","V59") predictions=predict.gam(test,c(matpdat,matpdat2),type="link",se.fit=TRUE) However, I receive the following error: Error in model.frame.default(ff, data = newdata, na.action = na.act) : invalid type (list) for variable 'matb' I have also tried combining the two matrices into a data frame, but I receive the same error using the following code: predictions=predict.gam(test,data.frame(c(matpdat,matpdat2)),type="link",se.fit=TRUE) I know that predictions are possible, given that if I do not specify the prediction values, the GAM. I'm not sure how the data matrix is supposed to be set up. I searched the MGCV documentation and I also searched the forums and google, but I was unable to find an example of someone making predictions from smooths of vectors. I would appreciate any help! Thanks! Nick -- Nicholas C. Jacobson Doctoral Student in Clinical Psychology 378 Moore Building The Pennsylvania State University University Park, PA 16802-3103 Phone: 814-863-0115 Email: njacobson at psu.edu Website: nicholasjacobson.com [[alternative HTML version deleted]]